Re: [ kvm-Bugs-2907597 ] qemu vnc server clips at 2560x1600

[Anthony Liguori <anthony@codemonkey.ws>]

On 01/10/2010 10:30 AM, Avi Kivity wrote:
> On 01/10/2010 06:26 PM, SourceForge.net wrote:
>> Initial Comment:
>> So I am running using the VESA driver to run an Ubuntu 9.10 guest at 
>> 2560x1600 (I had to modify the xserver-video-vesa package to remove 
>> an internal screen limit of 2048x2048 in the xorg vesa driver) and 
>> everything works great except that the qemu vnc server appears to 
>> clip at this resolution. The problem goes away if I run 1900x1200 and 
>> it doesn't change if I run 16bit depth or 24bit depth.
>>
>> I have attached two screenshots, the first is vncing directly into 
>> qemu (which exhibits the problem) and the second is vncing to a vnc 
>> server I have running in the guest which doesn't have the problem.
>>
>> I poked around in vnc.c and couldn't see any limits but I feel like 
>> its a buffer limit of some kind.
>>
>> Also if you look very closely at the first image you can see that the 
>> first row is drawn correctly all the way across but subsequent rows 
>> are not.
>>
>> If you need more information doesn't hesitate to ask.
>>
>
> Anthony, can you take a look at this?  Seems like a serious issue, 
> could find nothing obvious in vnc.c.

VNC_MAX_WIDTH and VNC_MAX_HEIGHT in vnc.h are currently defined to 
2048.  We do dirty tracking with a bitmap and that bitmap is currently a 
fixed size.

2048 is bigger than any physical screen that I know of so I assume this 
is a multiple monitor scenario.  Long term, I think exposing multiple 
monitors to the guest is a better approach for this kind of functionality.

Since these resolutions for a single screen don't really exist, this is 
largely an untested path within the guest.

Regards,

Anthony Liguori